Coriolis flow meter can be categorized into straight tube type and curved tube type according to the flow tube shape. For the straight pipe type flow meter with single-tube structure or double-tube structure, the strain which is caused by the tube expansion when heated and the change of the working pressure is very hard to compensate. This could lead to the worse repeatability and lower accuracy. Thus the straight pipe type Coriolis flow meter can be hardly used under the condition that varies greatly in temperature and pressure.
The curved tube type coriolis flow meter adopts tube of different shapes, including U-shape, Δ-shape, Ω-shape, single spiral shape etc. The coriolis flow meter with Δ-shaped, Ω-shaped or single spiral shaped flow tube is not widely used, because the flow tube of those shapes is longer or with relatively small inner turning angle. As a result, the pressure loss is larger, the shaping of the flow tube is harder, and the measured range is shorter. The popular U-shaped configuration also has some disadvantage, such as comparatively high pressure loss, low working frequency, and relatively large in size.
There is therefore a need for a new type of flow tube which avoids the drawback of the straight tube type, and is greatly improved compared with other curved tube type Coriolis flow meter.